中国东部新生代火山岩K-Ar年代学及其演化

K-Ar GEOCHRONOLOGY AND EVOLUTION OF CENOZOIC VOLCANIC ROCKS IN EASTERN CHINA

对中国东部新生代火山岩140多个K-Ar年龄测定表明:新生代火山活动具有多期多旋回的特点。呈NE向带状分布,有中心时代老、两侧新的变化趋势。本区火山岩主要属拉斑系列和碱性系列玄武岩,由老到新,碱性有逐渐增强趋势。上述规律受全球板块运动和区域性固有构造格局的双重控制。

The Cenozoic volcanic rocks widespread n eastern China constitute an important part of the circum-Pacific volcanic belt.This paper presents more than 150 K-Ar dates and a great deal of petrochemical analysis data from the Cenozoic volcanic rocks distributed in Tengchong, China's southeast coast, Shan-dong, Hebei, Nei Monggol and Northeast China. An integrated study .shows that ubiquitous but uneven volcanic activities prevailed from Early Tertiary to Holocene, which are characterized as being multi-episodic and multicycled. For example, in Paleocene (67-58 Ma), Eocene (57-37.5 Ma), Miocene (22-18, 16-19 Ma), Pliocene (8-3 Ma), and Early Pleistocene-Middle Pleistocene (1.2-0.5 Ma) there was an upsurge of volcanism, while in Oligocene there was an intermittent period. Spacially, the older Early Tertiary volcanic rocks are distributed within the region or in the central part of the NE-NNE-striking fault depres-sion, while the younger Later Tertiary and Quaternary volcanic rocks are distributed on the eastern and western flanks. Petrologically, they belong essentially to tholeiite series and alkaline series basalts with alkalinity increasing in the rocks ranging from old to young.The above regularities arc controlled by both global plate movement and regional inherent tectonic pattern.